Enameling apparatus

ABSTRACT

A method and apparatus for enameling metallic products such as cast iron bathtubs wherein the product to be enameled is mechanically conveyed to a preheating tunnel furnace where it remains sufficiently to reach a desired temperature. Then the product is automatically conveyed to a dredging station and oscillated during which enamel is mechanically distributed on the entire product from a dredging element which moves relative to the movement of the product. After application of the enamel, the product is conveyed to an enamel firing furnace and finally it is conveyed to a cooling station.

United States Patent 72] Inventors Robert Le Heron [56] References Cited Neuilly sur Seine; UNITED STATES PATENTS g ;E F'ederlc 707,490 8/1902 Zwermann 118/308 1 l N 2 2,435,931 2/1948 Schweitzer..... 118/321X [2 1 P Se 12 1967 2,821,158 l/1958 Brown m1 ll8/56X [22] 1 2,926,627 3/1960 Demorest et 81.... 1l8/308X [451 16,1971 3 132 038 5/1964 Ward 1l8/308X blissements Porch [731 Asslgnee 5;? France 3,191,574 6/1965 Robertson ll8/308X [32] Priority so .19,1966 Primary ExaminerJohn 1 McIntosh [33] France Attorney-Beveridge & DeGrandi [31] 76,856

ABSTRACT: A method and a paratus for enameling metallicv P products such as cast iron bathtubs wherein theproduct to be enameled is mechanically conveyed to a preheating tunnel [54] ENAMPUNG APPRAZTUS furnace where it remains sufficiently to reach a desired tem- 15 a s Drawing Flgs' perature. Then the product is automatically conveyed to a [52] US. Cl.... 118/308, dredging station and oscillated during which enamel is 118/313, 118/318, 118/326, 118/500 mechanically distributed on the entire product from a [51] Int. Cl B05c 5/00 dredging element which moves relative to the movement of [50] Field of Search 118/53, the roduct. After a lication of the enamel, the product is P PP 326, 319, 500, 320, 321, 308, 56, 313, 318; conveyed to an enamel firing furnace and finally it is conveyed 134/ l 61 to a cooling station.

11 Sheets-Sheet l INVENTORSZ RhBERT Le HERON,

HHROLD Le HERDN,

gmuos Sm. m.

REEERH. Le oucH PD Patenm Mam 16, 1971 ll fime he t i Rwam" LQ HERON,

HWWD Le Hemw, @mum STEL, Fmwme w WWW Patented March 16, 1971 11 Sheets-Sheet 4 amt Patented Mar;h16,1971 3,510,451

11 Sheets-Sheet 5 INVENTORSI- ROBERT Le HERON) HAROLD Le HERON, cmuos 1.11 1-, &

- FREDERIC L BoucHARt 1 g r m y Rmnmd March 16, 1971 3,570,451

11 Sheets-Sham a I I I Imem'ms: Vo'aewr Le Hume, H-Fmow L Hmm,

amuse fimrrmm FREDERm Le QHM'ZD Pitented March 16, 1971 3,510,451

ll Sheets+Sheet '7 INVENTORs: 'Rosem Le HEQo H9900) Le HmoN,

61.31406 SnLTL'L, FEEDER". Le BQACHRRD Patented March 16, 1971 3,570,451

11 Sheets-Sheet 8 INVBNTDRS 'Rotsem' Le HmzoN, HHRDl-D Le HFRDN, Cum as $Amm.,+ FEEDER at Le Eoucrmrm Rammed 116, 1971 3,570,451

1.1 fillsaet hesat 9 Inuawrons a Roma-r Le HaRoN, Haun -n Le Hzrzm, Oman-a fi rmm -Fr anaml .umqw

Patented Marh1 6, 1971 I I 3,570,451

11 Sheets-Sheet l0 FIG 11 FIG. 13

ruvem'oks 2 Roma L Human! gm? owLi Hume.

mum; fimrrcu, FEEDER)! le Bouwnkc Patcnted March 16, 1971 3,570,451

IMEnTDRfi: fioanrzr L e HERM HHQDLD .L 9 Hana QLVMADE. Smnm FREDEm a Le ucMPD ENAMEMNG APPARATUS SUMMARY OF OBJECTS AND INVENTION This invention relates to a novel process and apparatus for enameling metallic pieces such as for example cast iron bathtubs.

To ensure a good appearance to cast iron articles intended specifically for sanitary equipment, a known procedure is to enamel the said pieces on the surface or surfaces that are to be protected against corrosion and present a sanitary and pleasing appearance.

It is also known that the enameling of metallic pieces, either by application of liquid enamel or by the so-called dry or dredging process, is a very delicate operation that requires skilled labor, entailing high production costs.

The present invention relates exclusively to the dredging process which consists in bring the metallic piece coated with a slip called ground to a temperature of the order of 900 C., with subsequent uniform distribution of powdered enamel on the surface to be enameled, and finally in ensuring the fusing down to a smooth surface by firing in a furnace. In the conventional process currently used, the enamel is applied to the piece by means of a dredge manipulated by an operator who is called the enameler. This operation demands a considerable expenditure of physical effort on the part of the enameler, ability to withstand heat, and remarkable dexterity, to obtain an equal distribution of the enamel, since the slightest false move on the part of the enameler results in rejection of the workpiece. The professional requirements imposed on the enameler are the basis of considerable difficulty in recruitment. Moreover, for large scale production, each enameler must have a separate work station with a rotary support, a handling fork and one or two furnaces that must be maintained at a temperature higher than that to which the bathtub must be raised for enameling, involving a considerable heat expenditure and the setting up costly recuperating apparatus. One of the notable features of the process of the invention is the replacing of the manual enameling operation by a mechanical process.

The subject of the present invention is a novel continuous dry process enameling of metallic pieces, specifically cast iron bathtubs, the process being characterized substantially by the fact that pieces to be enameled are conveyed mechanically from storage to the entrance of a preheating tunnel furnace in which the piece remains for the time required to reach the desired temperature; the preheated piece is automatically conveyed to a station for mechanical distribution of the enamel; the piece and the enamel distributing dredge are constrained to execute a relative motion in the course of which the totality of the points of the surface pass under the enamel dredge or dredges at a uniform distance; the piece is then conveyed to the enamel firing furnace; and after firing the piece is extracted and moved on a cooling line.

The advantages of the process of the invention over the conventional manual operation described above reside substantially in the following points:

I. The requirement of skilled labor is eliminated.

2. The continuous preheating of the bathtub makes it possible to utilize the hot gases of the hottest part of the furnace for the preheating and to return these gases to the ambient air when they have released their calories to the tubs in the course of preheating.

. The rhythm of production is governed solely by the time of automatic dredging of the enamel, and is in no way subject to physical capabilities of works and particularly their ability to withstand heat.

4. The very fast production tempo that is obtained by application of the process of the invention, with a single tunnel furnace, one smooth-surfacing station and a simple furnace with a single compartment, makes it possible to produce as much as several conventional modern setups. This fast tempo allows a high degree of mechanization which is difficult to conceive for an enameling station that operates only intermittently. This is equally true of all the handling apparatus of plants with related work sequences, which justifies automation.

5. Use of a single enameling station for large scale production allows a substantial reduction of enamel losses in the dredging operation.

6. Since the production of bathtubs is continuous and the takeoff of the said tubs is localized at one well defined point, the cooling of the tubs can be effected logically and in a controlled manner, which is technically desirable but not practically attainable in conventional manual operations because of the dispersion of discharge points of the finished tubs.

In a preferred embodiment, the tunnel preheating furnace encloses carriages on which the workpieces are mounted, the issuing of a carriage and the preheated piece that it bears coinciding substantially with introduction of a carriage bearing a cold workpiece at the outer end of the tunnel. The tunnel furnace delivers a carriage and a preheated piece each time that it has been possible to empty the mechanical enamel dredging station on the production line. In other words, the rhythm of production is controlled by the tempo of the mechanical dredging station on the line.

It is fitting to point out that one or more successive dusting operations can be effected on the same workpiece, according to the desired thickness of the enamel. In the case of multiple dredgings the plant must of course have a number of fusing down furnaces to correspond to the number of layers of enamel, this provision avoiding a break in the continuity of the process.

The number of carriages in the tunnel furnace is such that each carriage has a sufficient residence time in the tunnel furnace to reach the desired temperature.

In the special case in which the pieces to be enameled are bowl shaped, e.g. bathtubs, the enameling station has a plate which executes a complex movement. The tub to be enameled is fixed on the said plate, and above it the vibrating screen that distributes the powdered enamel executes only horizontal movements. The motion of the plate supporting the tub to be enameled is so arranged that the dredge remains at a substantially uniform distance from the surfaces on which it deposits the powdered enamel, and it moves with reference to the said surfaces at a substantially constant speed. To do this, the plate on which the bathtub is fixed is inclined at about 45 with reference to the dredge, and it moves in rotation around a first axis that itself rotates around a second axis which is fixed and parallel to the first, the said first rotation occurring at a speed that is half that of the second rotation, and in the opposite direction.

It may be emphasized that the dredging of the enamel is accomplished simultaneously on one sidewall and on the bottom part of the bathtub. This is an interesting feature of the device of the invention because customarily the enamel dusting is effected first either on the sides or on the bottom of the tub but not on both at the same time. It may further be pointed out 'that the vibrations impressed upon the dredge are so controlled that distribution of the powder is slowed in proportion to the thickness of the enamel layer already on the tub.

Moreover, the enameling station is furnished with a dredge device that follows the edges of the tub at a substantially constant distance and speed, being controlled by a cam arrangement that is integral with the drive of the above mentioned supporting plate.

The conveying of the dredged tube is effected by an automatic charging platform that moves into the fusing down furnace, while another platform effects the discharging from the furnace and setting in place on the cooling line.

The present invention also relates to devices for conducting the above described process, particularly the combination of a mechanical charging conveyor for a tunnel furnace, the tunnel furnace supplied by the said conveyor, a mechanical discharging conveyor, a device for return of the carriages that constitute the supports of the pieces to be preheated in the tunnel furnace so that the said carriages moved in a closed circuit. The invention further relates to a station for mechanical enameling, comprising a support plate for the pieces to be enameled and one or more dredges for distribution of the powdered enamel, the said dredges being constrained to execute, with reference to the workpiece, a relative movement at substantially uniform distance and speed, a conveyor which allows supply of one or more fusing down furnaces, a conveyor effecting discharge of the said fusing down furnace, and a cooling line.

DETAILED DESCRIPTION In order to make the invention more understandable, there will now be described as nonlimitative illustration an embodiment which is shown schematically in the attached drawings.

In the drawings:

FIG. 1 is a schematic plan view of a setup according to the invention, which makes possible the enameling of cast iron bathtubs previously coated with a slip ground formed by a mixture of silicates;

FIG. 2 shows the conveyor which loads a bathtub onto a carriage;

FIG. 3 shows in elevation the pusher device that introduces a bathtub loaded carriage into the tunnel furnace;

FIG. 4 shows the extractor for removal of the empty carriage from the tunnel furnace after removal of the preheated tub borne by the said carriage;

FIG. 5 shows a transverse section of the tunnel furnace;

FIG. 6 shows a carriage for conveying the bathtub through the tunnel furnace;

FIG. 7 shows the handling device for extraction of a preheated tub from the furnace;

FIG. 8 shows in axial section the drive device for the supporting plate of the enameling station;

FIG. 9 is a plan view of the device of FIG. 8;

FIG. 10 shows a transverse view of the whole enameling statron;

FIG. 11 is a plan view of the whole enameling station;

FIG. 12 is a plan view of the conveyor that carries the dredged bathtub into the fusing down furnace;

FIG. 13 is a view in elevation of the device of FIG. 12.

With reference to the drawings, it will be seen that on the overall diagram in FIG. 1 numeral 1 designates the conveyor that allows loading of a bathtub, to convey it above a carriage on which it is placed at the station designated 2. The carriage loaded with the bathtub is conveyed on a transfer mechanism 3 to the furnace station designated 4. The furnace station 4 is opposite the entrance of tunnel furnace 5 from which discharge is effected at a transfer station designated 6, where the bathtub that was preheated in tunnel furnace 5 is removed. Additionally at station 6, the carriage which held the discharged tub is transferred by mechanism 7 similar to entrance transfer mechanism 3, to a return line 8 which leads in reverse direction back to station 2. The preheated bathtub discharged from the tunnel furnace is taken to an enameling station generally designated 9. After dredging with powdered enamel, the bathtub is taken up by a conveyor 10 which delivers it to the so-called fusing down furnace 11. Removal from furnace I1 is effected by a conveyor 12 which delivers the bathtub to a cooling line 13.

Stations 4, 5, 6, 9 and 13 are aligned. In contrast, station 11 is off to the side so that charging and extraction from the fusing down furnace are effected through the same door of the furnace, this arrangement having the advantage from the point of view of heat economy, since the fusing down furnace has only one door.

Conveyor device 1 and the station for loading carriage 2 are shown in detail in FIG. 2. In this FIG, it is seen that the device is constituted by a movable trolley apparatus that moves on an overhead rail 14 such as may be on the ceiling of the shed that shelters the equipment. The movable apparatus 15 supports a rhombus linkage connected to apparatus 15 by a shaft 16 that forms one of the apexes of the said rhombus. The apex opposite shaft 16 is connected to a plate 17 by a shaft 18. The two other apexes of the rhombus are connected, the first, 19, to piston 20 of a hydraulic or pneumatic jack, and the second, 21, to body 22 of the said jack. In the arrangement described below, all the jacks are assumed to be hydraulic, but it is quite clear that the said jacks could also be pneumatic or other suitably powered jacks. The above mentioned jack is additionally supported at its end opposite that which supports shaft 21 by a rod 23 which with rod 24 connecting shafts 16 and 21 forms two parallel arms of an articulated parallelogram whose other two parallel arms are on the one hand mechanism 15 and on the other the hydraulic jack 22. This assembly is substantially symmetrical with reference to the longitudinal axis ofjack 22, i.e. there is a rod 25 symmetrical to rod 23, and a rod 26 symmetrical to rod 24.

Plate 17 supports two skis 27, below its opposite sides, and parallel to jack 22. The skis are separated by the width of the bathtub to be enameled. The skis 27 engage under the edges formed by the upper part of the tubs. A bathtub is drawn in position for treatment, designated 28 in FIG. 2. This bathtub is set onto the two skis 27 either manually or automatically by any appropriate means.

Bathtub 28 when it is brought to the conveyor is preferably covered with a layer of slip called ground, but it is obvious that the presence of this layer is in no way necessary to the process of the invention. The ground comprises a mixture of silicates of the type customarily used.

Mechanism 15 presents an arcuate element 29 on which electric contacts are placed, for control of the operation of jack 22. It can move along the rolling path 14 to the loading station designated 2 in FIG. 1. It thus arrives above the point at which a carriage designated 30 has been placed.

Carriage 30 is mounted on four rollers 31 which allow it to move on rails 32. It comprises two vertical uprights 33 whose upper ends are connected by two horizontal bars 34 between which there are stretched refractory steel wires 35. The length of bars 34 is such that the assembly constituting the bars and wires 35 forms a cradle for bathtub 28.

The position of carriage 30 in loading station 2 is ensured by a stop 36 against which the said carriage is applied by a control arm 37. When the carriage is in good position, it is on a transfer unit designated 3: the translation of the said transfer unit 3 is perpendicular to rail 14.

Transfer unit 3 is mounted on rollers 38 whose path is designated 39. The displacement of the transfer unit is as far as the station designated 4 in FIG. 1. Station 4 is just opposite the entrance of tunnel furnace 5.

A stop device ensures'alignment of the portions of rail 32 supported by the transfer unit 3, on which rail portions carriage 30 can roll, and rails 40 which allow introduction of carriage 30 into tunnel furnace 5. The said rails 40 are symmetrically disposed with reference to the axis of the tunnel furnace, and parallel to the said axis.

The tunnel furnace is provided at its entrance side, i.e. on the side of station 4, with a double door 41 which is controlled transversely by a hydraulic jack. In addition, the furnace is separated into two parts by a horizontal insulating partition 42 (see FIG. 5) presenting along the furnace axis, a slot that affords passage for uprights 33 of carriages 30. Above wall 42 is the hot part of the furnace. Below said wall there is the rolling part of the carriages. To ensure a seal between the two zones from the point of view of thermal insulation, there is a sand joint formed by two gutters 43 filled with sand and by two angle elements 44, one of whose flanges is embedded in the gutter, the other being connected to uprights 33 of the carriage.

In the lower part of the tunnel furnace 5 and in the entrance zone there is a pusher designated 45. Device 45 comprises a movable element sliding along rails 40 of the furnace and presenting at the forward part, i.e. on the side of station 4, a hinged self-locking prop 46. Pusher 45 is shown in detail in FIG. 3. Its movable element comprises two side pieces 47 on which there are rollers 48. The. side pieces 47 are interconnected by steel bars 49, the spacing of the said bars being such that the bar assembly 49 forms a sort of rack which engages a control pinion 50 whose drive reduction element is designated 51.

Prop 46 is placed on one of the side pieces 47 and when pusher 45 is in its extreme forward position it engages stop 52 borne by transfer unit 3. This contact is only effected, of course, if transfer unit 3 is at station 4, i.e. if it has conveyed carriage 30 to a point opposite the entrance of tunnel furnace 5. The apex of prop 46 bears a damping device 53 which can be applied to the frame of carriage 30 when pusher 45 moves toward the interior of the furnace, which allows introduction of the said carriage into tunnel furnace 5. When the said carriage is completely introduced into the furnace, prop 46 abuts against a fixed rod 54 inside the tunnel furnace, said rod 54 causing the folding of the prop and the lowering of damping element 53.

The outlet from tunnel furnace 5 is closed by means of a double door 55 controlled by hydraulic jack and identical with door 41. An extractor designated 56 effects the exit of carriages 30. Device 56 delivers carriage 30 issuing from the tunnel furnace onto a transfer unit 7, the loading of the carriage on the transfer unit being accomplished at the station designated 6 in FIG. 1. The transfer unit 7 is identical with transfer unit 3 at the entrance to the tunnel furnace. It comprises rollers 38a which move on a rolling path 39a which is parallel to path 39, and disposed symmetrically thereto with reference to the center of the tunnel furnace. The transfer unit supports carriage 30 by rails 32 which receive rollers 31 of carriage 30. Rails 32 are positioned with a very slight incline, of the order of 1 percent, on transfer unit 7, so that carriage 30 issuing from the furnace will not tend to pass through station 6 and so that the said carriage will remain in place on the transfer unit when it is delivered there by extractor S6.

Extractor 56 comprises two wheels 57-58 which are connected by a chain 59. The extractor parallels rails 40 of tunnel furnace 5, on one side of the track formed by the said rails. Chain 59 has three blocks 60 which are perpendicular to the extensions of the axles of wheels 31 of carriage 30, which extensions are designated 31a in the drawing. The three blocks 60 are spaced at equal distances along chain 59 whose total length is so calculated that when the extractor is not operating one of blocks 60 is near extension 31a of one of the axles of carriage 30 inside the furnace, and so that another of the blocks is then in contact with extension 31a of one of the axles of carriage 30 on transfer unit 7, said transfer unit then being at the station designated 6 in FIG. 1. The transfer unit 7 can execute a movement of translation that is identical to that of transfer unit 3, so as to being carriage 30 that it supports into the return track designated 8 in FIG. 1. The return track 8 comprises rails 32 which end at loading station 2. Transfer unit 7 delivers carriage 30 that it bears apoint opposite said rails 32. On the return track 8 the movement of the carriage is effected by a block chain similar to that of extractor 56.

The bathtub borne by the carriage is taken before extraction of the carriage by a conveyor designated 61 shown in details in FIG. 7. it moves in translation on an overhead rail 62 placed on the ceiling of the shop where the apparatus is installed. Rail 62 is located in the extension of the axis of tunnel furnace 5. A movable assembly 63 rolls on rail 62 and has a rack device that allows vertical movement of a plate 64 which is a support for a fork 65. The vertical clearance of plate 64 is adequate to allow fork 65 to descend to the desired height to penetrate inside tunnel furnace 5 when discharge door 55 is open, and to raise the tub at the output of the tunnel furnace. The movement of assembly 63 along rail 62 will bring the tub to the enameling station designated by 9 in H6. 1. The vertical translation of plate 64 allows fork 65 to deposit the bathtub on the bathtub support at the enameling station.

When the dredged enamel has been dusted onto bathtub 28 which is treated at enameling station 9, the tub is taken by a transfer unit designated (FIGS. 12 and 13) which moves on two horizontal ground rails 66. It comprises a principal frame 67 rolling by means of rollers on rails 66, the movement of translation of the principal frame being controlled by reducing gear 68. On the principal frame there are mounted two crosswise rails 69 on which there is a secondary frame 70 having an upright element 71 in its central zone, the said upright being rotatable about its own axis. The transverse translation of secondary frame 70 is controlled by a reducing gear 72 and the rotation of upright 71 is controlled by a reducing gear 73, by means of a toothed crown 74. On upright 71 there is a movable assembly 75 which supports a fork 76. Assembly 75 can move in vertical translation on upright 71 by means of rack 77. its movement is controlled by a gear 78 which is rigidly fixed on assembly 75.

Transfer platform 10, by its translation and rotation, makes it possible to take a bathtub at the enameling station and deliver it opposite the door 79 of fusing down furnace 11 in which it introduces the tub after the door 79 is opened. Door 79 is controlled by a hydraulic jack. Tub 28 is placed in the fusing down furnace 11, on a fixed cradle 80. The removal from the furnace after firing of the enamel in furnace 11 is e ffected by a platform 12 which is absolutely identical with transfer platform 10 described above. The rails under platform 12 are extensions of the rails under transfer platform 10. Platform l2 deposits the enameled tub on the cooling line, which is conventional type, designated 13 in FIG. 1. As shown in FIG. 10, enameling station 9 of F IG. 1 has substantially two devices, the dredge designated 81, and a drive for the bathtub designated 82. Dredge 81 comprises a carriage mounted on rollers 83 which moves in translation on rails 84 whose direction is perpendicular to the axis of tunnel furnace 5. The motion of the dredge on its rails 84 is controlled by a jack 85. The carriage hasat its front part a screen 86 which is out of plumb and which is caused to vibrate by means of a pneumatic device 87. Supply to the screen is effected by a distributor 88 from a hopper 89 connected to distributor 88, via flexible hose 90. Screen 86 as well as its vibrator 87 and its distributor 88 can be moved, with reference to the carriage that supports them, in a horizontal movement which is closed to a translation substantially perpendicular to the direction of rails 84. The said movement is a rotation of slight angular amplitude and large radius. Screen 86 is furnished with a cooling device. Since hopper 89 distributes the enamel to screen 86 as a fine powder, the work station is surmounted by a dust aspirator hood 91 having a filter that retains the aspirated enamel. I

Referring to FIGS. 8, 10 and 11 the drive device 82 for the bathtub is located opposite the end of rails 84. Drive device 82 is formed by a circular plate 92 on which there is mounted a bathtub support 93, formed by a single sheet in the form of the tub to be treated. Bathtub support 93 is fixed on plate 92 so that the center of the bathtub approximately coincides with the center of the plate.

Plate 92 is mounted on a shaft 94 that drives it in rotation. The movement of shaft 94 is double: on the one hand it turns on itself and on the other hand it is driven in rotation around shaft 95 (see H6. 8) from which the movement is imparted to a gear designated 96. Shaft 95 is connected to a reducing gear 97.

Gear 96 is formed by a fixed casing 98 which supports a fixed gear wheel 99. On fixed casing 98 there is a movable casing 100 which is rigidly fixed to shaft 95, the said casing supporting a satellite 101 on shaft 102 on which there is also mounted a pinion 103. Casing 108 has at its upper part a casing cap 104 in which there is mounted shaft 94 which is connected to and controls plate 92. At the end of shaft 94 there is a toothed pinion with pinion 103 of satellite shaft 102. (lasing cap 104 can rotate about the axis of satellite shaft 102, since its position on casing 100 is adjustable but locked once the adjustment has been made, by means of bolts 106. The adjustment of casing cap 104 on movable casing 100 makes it possible to shift shaft 94 with reference to shaft 95, with the said shaft still driven in rotation.

Consequently shaft 94 executes a circular or revolving motion around shaft 95 so that movement of bathtub support 93 is the resultant of two circular motions, one around shaft 94 and the other around shaft 95, the two shafts being parallel but staggered with reference to each other. Moreover, these two movements of rotation are effected in opposite direction, and the ratios of gears 99, 101, 103 and 106 are selected so that the rotation around shaft 94 is at half the speed or rotation of that around shaft 95.

Referring to FIG. 8 gear 96 is mounted on a frame 107 that can swing by more than 45 and around a horizontal shaft 108 so that plate 92 can be either horizontal or inclined at 45 in the direction of dusting device 81.

Referring to FIG. 10, on thedrive shaft of gear 96 there are two cams, 109, 110. Cam 109, via a conventional cam follower, drives a duster 111 which is constrained because of the configuration of cam 109 to follow the edges of bathtub support 93 and consequently the edges of the tub during the whole movement of support 93. Cam 110 controls, via a cam follower, the movements of translation of screen 86 with reference to duster 81.

OPERATION As will now be described, the assembly allows an enameling cycle which is continuous and without manual operations. Bathtub 28, covered with its ground slip is delivered to the station designated 1 in FIG. 1 on skis 27 of the conveyor. By means of jack 22, plate 17 is raised to lift tub 28 and unit is moved along rail 14 to station 2 above carriage 30 which is waiting at this station. When safety arm 37 has ensured the position of carriage 30, the lowering of the tub is effected by jack 22, until the bathtub rests on carriage 30 by means of bars 34 and cross wires 35. The movable unit then moves in reverse and returns to station 1 where it is ready to receive another tub.

Transfer unit 3 then moves from station 2 to a point opposite the entrance to tunnel furnace 5, rolling on its track 39. At the conclusion of the movement, reducing gear 51 drives the pusher 45 in the direction of transfer unit 3 until prop 46 comes into contact with stop 52 borne by the transfer unit, and locks it in elevated position.

The hydraulic control jack then opens door 41 of tunnel furnace 5 and, via reducing gear 51 and the wheel and rack arrangement 50-49, drives pusher 45 toward the interior of the furnace. In this movement damping element 53 is applied against the frame of carriage 30 that it drives and, since the transfer unit has arrived a point where the portions of rails 32 that it carries are opposite rails 40 which penetrate into the furnace, carriage 30 moves, rolling onto the said rails 40. When carriage 30 has entered the furnace, doors 41 close again behind it.

In the course of this forward movement the carriage comes into contact with the carriage ahead, which is already in the furnace, and pushes the said carriage by a length equal to its own driven length. At the end of the movement of pusher 45, prop 46 abuts against bar 54 which folds the prop and causes the release of damping device 53 and stops the drive of carriage 30. Given that the tunnel furnace contains carriages 30 one behind the other, it will be appreciated that the entry of one of the carriages causes the advance of all the others.

But it is appropriate to emphasize that the entrance of a carriage 30 does not cause the exit of another carriage 30. This exit is effected by the extractor 56 before a new carriage is introduced into the furnace. This sequence of operations occurs as follows: door 55 controlled by its hydraulic jack is opened and conveyor 61 advances along its rail 62 at the same time that fork 65 is lowered to be able to enter furnace 5. The two arms of fork 65 engage tub 28 under the upper edges and when plate 64 is raised by the rack device that controls it, the tub is lifted so that it no longer rests on its carriage support 30. The heating of furnace 5 and its length are so calculated that the ground" slip covering the bathtub is fired and the tube as a whole is heated to a temperature of about 92 C.

Once conveyor 61 is loaded with its bathtub, it moves backward very rapidly along its rail 62 to arrive above enameling station 9 before the tub has time to cool off. The dredging with enamel must take place preferably between 850 and 920 C. The fork 65 then is lowered, to deposit tub 28 inside bathtub support 93; The descending motion of fork 65 then continues, to release the tub completely, and the conveyor receives a supplementary movement of withdrawal so that the arms of the fork are disengaged from the upper edges of the tub. Plate 64 then rises and the conveyor unit 61 moves forward in the direction of tunnel furnace 5.

The bathtub which has been loaded on its support 93 has released a carriage 30 which is still inside tunnel furnace 5. The extractor 56 enters into action to remove the said carriage from tunnel furnace 5. Wheels 57 and 58 drive chain 59, and immediately a block comes into contact with extension 31a of the front axle of carriage 30 that is to be evacuated. Block 60 draws the carriage up to the portions of rails 32 that are borne by transfer unit 7. Doors 55 of furnace 5 are then closed and transfer unit 7 moves on its rolling track 39a to deliver carriage 30 opposite rails 32 of return track 8. When the transfer unit is stopped in a good position, the block chain of the return track starts and pulls carriage 30 on return track 8 back to station 2. The transfer unit 7 then returns to station 6 opposite the exit of tunnel furnace 5. When the carriage reaches station 2 it is locked in position by control arm 37 and is applied against stop 36 at the same time that the block chain of the return stops. The carriage is thus in position thereafter to receive another tub to be inserted in tunnel furnace 5.

The bathtub loaded into its support 93 is then titled by 45 in the direction of dredging device 81 by swinging plate 92 45 around axis 108. Dusting device 81 which was in a rear position moves toward the bathtub until screen 86 is engaged inside the said tub without touching any of its edges, however. The vibrator 87 then begins to function at the same time as the supply 88 to the screen. At this moment motor 97 is started, imparting the bathtub 28 the movement of double rotation that was described above. In the course of this movement and because of the fact that the two rotations are in opposite directions, one rotation being at half the rate of the other, the trace ofa fixed point in space on the tub, seen in plane view, is an ellipse. The dredging cycle comprises on the one hand one rotation in one direction during about one-half the dredging time and on the other hand a rotation in the other direction during the rest of the dredging time. The reversal of the direction of rotation is caused by a reversal of the phases of the drive motor and it is possible to regulate as desired, according to the results obtained, the number of turns to be effected in one direction and the number of turns to be effected in the other direction. It has been observed that good results are obtained by dredging during four turns in one direction and four turns in the other direction, the whole operation lasting about 2 minutes. The vibration of device 87 makes it possiinto account the possibility that the enamel powder may cling to the walls on which it falls. Further, it is appropriate to point out that it is necessary to cool screen 86 which during its operation is inside a bathtub that is preheated to about 900 C.

The rhythm of the enameling station determines the number of carriages 30 inside tunnel furnace 5,- given that the time of heating necessary for the carriage support of the tub is on the order of magnitude of 20 minutes. In the embodiment described, the tunnel furnace contains nine carriages.

The motion of screen 86 with reference to the tub ensures a good distribution of the enamel powder which is delivered to the screen by storage hopper 89. The motion is synchronized with the rotation of bathtub 28 by means of cam and of the cam follower associated therewith. It is important that the distribution be perfectly uniform over the whole surface of the bathtub to avoid the appearance of flaws upon firing the enamel. Further, device 111, actuated by its cam follower and the associated cam 109, follows the upper edge of the tub, to

dredge the said edges. Finally carriage 81 is actuated by a movement of translation on its rails 84, which movement is relatively small, and reciprocating.

Dust from the dredging of the bathtub with enamel powder is aspirated by hood 911 above work station 9.

When the dredging of the bathtub is completed, plate 92 stops in its original position, dusting carriage bl withdraws to the rear position and the entire assembly including motor 97, gear 96, plate 92, bathtub support 93 and dredged tub 28 pivots about shaft 108 until plate 92 is horizontal. Transfer platform til then moves forward with its fork 76 in low position until the arms of the fork are beneath the upper edges of the bathtub. Mechanism 75 is then raised by vertical translation through gears 77,78 and the secondary carriage 70 is moved by translation on rails was far away as possible from fusing down furnace 11. At this moment upright 71 is driven in rotation by assembly 73, 74 so that fork 76 takes a position perpendicular to the axis of tunnel furnace 5. The transfer assembly then moves on rails 66 until fork 76 is opposite the door 79 of fusing down furnace 11. This door, operated by a hydraulic jack, then frees the entrance to the furnace and secondary carriage 70 moves to insert the bathtub supported by fork 76 into the furnace. Mechanism 75 has lowered, so that fork 76 delivers bathtub 28 into cradle 80 in the fusing down furnace, and then secondary carriage 70 withdraws as far as possible, door 79 of the furnace closes, upright 71 pivots by 90 in the direction opposite that of its former rotation, secondary carriage 70 resumes its midposition and principal carriage 67 again advances to return to the waiting position near enameling station 9.

At the end of about 2 minutes the firing of the enamel that dredges tub 28 is completed inside furnace 11 in which a temperature of about 930 C., prevails. It must be emphasized that this firing is effected during the time of dredging of the tub which is at the enameling station 9: at the end of the required 2 minutes, platform 12 which is identical with platform effects the same maneuvers as 10 in the reverse direction, to extract tub 28 from furnace ll and deliver it to a cooling line 13. The enameling of the bathtub is then completed.

The controls of the various stations of the enameling line together are synchronized in time, and the cycle of operation of the plant is completely automatic. it is thus to be noted that this enameling process eliminates all manual labor and allows continuous operation. It is obvious however that certain operations in the cycle could be done manually without any major difficulty, to the extent that is desired to make the plant entirely automatic or not. For example, the operation of v removal of the bathtub from the fusing down furnace, and the dredging of the upper edges of the bathtub with enamel powder could be done by hand.

it is understood, of course, that the embodiment described above is in no way limitative and can have any desirable modification without exceeding the scope of the invention. Particularly, by way of example, it would be possible to arrange two or more successive enameling stations on the enameling line, supplying a single fusing down furnace in the case in which distribution of enamel on the workpieces requires more time than the time required for firing the enamel. If on the contrary the firing time is longer than the time needed for mechanical dusting of the workpiece, two or more fusing down furnaces could be successively supplied by the same dredging station. It is also possible to conceive of replacing such a battery of fusing down furnaces with a tunnel furnace analogous to the one used for preheating, into which furnace the bathtubs dredged with enamel would be introduced as they emerged from the enameling station.

We claim:

l. A device for movably supporting a workpiece during an enameling or other material application process for evenly presenting various surfaces of the workpiece to an enamel or other material applicator; the device comprising in combination, a workpiece support member adapted to receive the workpiece, a first shaft secured to the workpiece support member generally at a central portion thereof, a casing having means mounting said first shaft for rotatable movement about the axis of said first shaft in one angular direction to rotate said workpiece support member in said one angular direction, a second shaft and means mounting said second shaft for rotation about its own axis spaced from and parallel to said first shaft, means connecting said casing to said second shaft to be rotatable by said second shaft in a second angular direction counter to said first angular direction to revolve said workpiece support member in said angular direction about said second shaft, gear means located in said casing interconnecting said second shaft and said first shaft to transmit motion from said second shaft to said first shaft to drive said first shaft in said first angular direction, and means for driving said second shaft about its own axes.

2. The device defined in claim 1 further including a frame supporting said second shaft, and means adjustably mounting said frame in an angular position for supporting the workpiece at an angle to the horizontal,

3. The device defined in claim 1 wherein said workpiece support member includes a bathtub holder having shape similar to a bathtub for receiving therein a bathtub to be enameled.

4. In combination with the device defined in claim 1, a screen for distributing an enameling substance to a workpiece, means supporting said screen in a position to overlie the workpiece, and means for vibrating the screen.

5. The combination defined in claim 4 further including a second screen for distributing enamel substance on the workpiece, and means for moving said second screen in translation over the workpiece.

6. The combination defined in claim 5 further including means synchronizing movement of said screens with movement of said supports, said last recited means including cams operated by said means for rotating said second support 7. The combination defined in claim 4 further including an aspirator hood having a filter located above said workpiece support member.

8. The combination defined in claim 4 wherein said means supporting said screen includes a conveyor movable between a retracted position away from said workpiece support member and an operative position adjacent said workpiece support with the screen extending at least partially over a portion of said workpiece.

9. The combination defined in claim 8 further including an enamel discharge means mounted on said conveyor, a supply containing enamel substance, and a flexible conduit interconnecting said supply and said discharge means, said discharge being positioned to introduce enamel substance onto said first screen for distribution on the workpiece to be enameled.

10. The device defined in claim 1 further including means for driving said first shaft at one-half the speed of said second shaft.

11. A powdering table for use in powder enameling of bath tubs and similar objects with an elongated shape, of the type wherein the table has a central shaft and is set at an inclined position of about 45 under a stationary powdering device and turned around the axis of its central shaft; the apparatus comprising a gear casing having means mounting said central shaft for rotation therein, a second shaft spaced from and parallel to said first shaft, means mounting said casing about said second shaft for rotation about the axis of said second shaft, and means for rotating said casing about the axis of said second shaft in the opposite direction and at twice the speed of rotation of the table about the axes of its central shaft, with a distance between the two parallel shafts determined so that at during each complete revolution of the table the inside surface of a bathtub supported on the table will pass substantially directly under the powdering device.

12. The apparatus defined in claim 11 including means for driving said second shaft in rotation and wherein said means for rotating said casing includes means operatively interconnecting said second shaft and said casing to drive the casing in response to rotation of said second shaft, and wherein there is further included gear means in said casing for driving said central shaft in response to movement of said second shaft and casing.

13. Apparatus defined in claim 12 wherein there is further included a third shaft mounted in said casing parallel to said central and second shafts, said casing is made up of upper and lower parts, said lower part being driven by said second shaft and said upper part having said central shaft mounted therein and being coupled on said lower part for adjustment about said third shaft to vary the distance between said central and second shafts, said gear means including a first gear fixed to said central shaft concentrically therewith, and a second gear 

1. A device for movably supporting a workpiece during an enameling or other material application process for evenly presenting various surfaces of the workpiece to an enamel or other material applicator; the device comprising in combination, a workpiece support member adapted to receive the workpiece, a first shaft secured to the workpiece support member generally at a central portion thereof, a casing having means mounting said first shaft for rotatable movement about the axis of said first shaft in one angular direction to rotate said workpiece support member in said one angular direction, a second shaft and means mounting said second shaft for rotation about its own axis spaced from and parallel to said first shaft, means connecting said casing to said second shaft to be rotatable by sAid second shaft in a second angular direction counter to said first angular direction to revolve said workpiece support member in said angular direction about said second shaft, gear means located in said casing interconnecting said second shaft and said first shaft to transmit motion from said second shaft to said first shaft to drive said first shaft in said first angular direction, and means for driving said second shaft about its own axes.
 2. The device defined in claim 1 further including a frame supporting said second shaft, and means adjustably mounting said frame in an angular position for supporting the workpiece at an angle to the horizontal.
 3. The device defined in claim 1 wherein said workpiece support member includes a bathtub holder having shape similar to a bathtub for receiving therein a bathtub to be enameled.
 4. In combination with the device defined in claim 1, a screen for distributing an enameling substance to a workpiece, means supporting said screen in a position to overlie the workpiece, and means for vibrating the screen.
 5. The combination defined in claim 4 further including a second screen for distributing enamel substance on the workpiece, and means for moving said second screen in translation over the workpiece.
 6. The combination defined in claim 5 further including means synchronizing movement of said screens with movement of said supports, said last recited means including cams operated by said means for rotating said second support
 7. The combination defined in claim 4 further including an aspirator hood having a filter located above said workpiece support member.
 8. The combination defined in claim 4 wherein said means supporting said screen includes a conveyor movable between a retracted position away from said workpiece support member and an operative position adjacent said workpiece support with the screen extending at least partially over a portion of said workpiece.
 9. The combination defined in claim 8 further including an enamel discharge means mounted on said conveyor, a supply containing enamel substance, and a flexible conduit interconnecting said supply and said discharge means, said discharge being positioned to introduce enamel substance onto said first screen for distribution on the workpiece to be enameled.
 10. The device defined in claim 1 further including means for driving said first shaft at one-half the speed of said second shaft.
 11. A powdering table for use in powder enameling of bath tubs and similar objects with an elongated shape, of the type wherein the table has a central shaft and is set at an inclined position of about 45* under a stationary powdering device and turned around the axis of its central shaft; the apparatus comprising a gear casing having means mounting said central shaft for rotation therein, a second shaft spaced from and parallel to said first shaft, means mounting said casing about said second shaft for rotation about the axis of said second shaft, and means for rotating said casing about the axis of said second shaft in the opposite direction and at twice the speed of rotation of the table about the axes of its central shaft, with a distance between the two parallel shafts determined so that at during each complete revolution of the table the inside surface of a bathtub supported on the table will pass substantially directly under the powdering device.
 12. The apparatus defined in claim 11 including means for driving said second shaft in rotation and wherein said means for rotating said casing includes means operatively interconnecting said second shaft and said casing to drive the casing in response to rotation of said second shaft, and wherein there is further included gear means in said casing for driving said central shaft in response to movement of said second shaft and casing.
 13. Apparatus defined in claim 12 wherein there is further included a third shaft mounted in said casing parallel to said central and second shafts, said casing is made up of upper and lower parts, said lower part being driven by said second shaft and said upper part having said central shaft mounted therein and being coupled on said lower part for adjustment about said third shaft to vary the distance between said central and second shafts, said gear means including a first gear fixed to said central shaft concentrically therewith, and a second gear fixed to said third shaft in mesh with said first gear, and wherein said means operatively interconnecting said second shaft and said casing includes a third gear fixed to said second shaft and a fourth gear fixed to said third shaft in mesh with said third gear.
 14. The apparatus defined in claim 13 including means for locking the upper part of said casing relative to said lower part in adjusted position.
 15. The apparatus defined in claim 11 further includes means for adjusting the distance between the axes of said central and second shafts. 